1. Field of the Invention
The present invention relates generally to control apparatus and method for controlling a position of an electromagnetically operated engine valve for an internal combustion engine with a position sensor and, particularly, relates to the controlling apparatus and method in which an output value of a position sensor to detect a displaced position of an armature with respect to a pair of electromagnets constituting the electromagnetically operated engine valve is retrieved and corrected during an engine start to eliminate an error in an output value of the position sensor.
2. Description of the Related Art
A Japanese Patent Application First Publication No. Heisei 11-81940 published on Mar. 26, 1999 exemplifies a previously proposed electromagnetically operated engine valve.
In such an electromagnetically operated engine as described above, a biasing force of a pair of springs causes a valve body of an intake or exhaust valve to be supported at a half open position (also called, a neutral position). Then, an electromagnetic force is acted upon an armature associated with the valve body so that the intake or exhaust valve is moved in either a maximum (or full) open direction or a closure direction. In such a kind of electromagnetically operated engine valve as described above, an initialization such that the electromagnetically operated engine valve is held at a full open position or the closure position is carried out before the engine is started. Thereafter, a power supply to a valve closing electromagnet is turned of f when the valve is to be opened. The biasing force of the pair of springs causes the valve body to be moved in the valve open direction. When a valve axle of the engine valve approaches sufficiently to a valve opening electromagnet and the power supply to the valve opening electromagnet is turned on, the armature is attracted onto the valve opening electromagnet and held thereat as the full open position. When the engine valve is to be closed, the power supply to the valve opening electromagnet is turned off and the valve axle (armature) is moved in the closure direction by means of the biasing force of the pair of springs. When the valve body is moved toward the valve closure direction and approaches sufficiently to the valve closing electromagnet, the power supply to the valve closing electromagnet is turned on and the valve body (armature) is attracted onto the valve closing electromagnet and held at the valve closing electromagnet so that the valve is held at the closure direction. Such a valve open-and-closure control for the engine valve as described above is, thus, carried out.
A control over the power supply turn-on-and-off for the valve opening electromagnet and the valve closing electromagnet is carried out in a feedback control mode such that while a position sensor is detecting a position of the armature, a velocity of the armature is made substantially equal to a target velocity thereof based on the position of the armature.
In the control over the power supply turn-on-and-off of the power supply, a velocity of each of the armature and the valve body to be reached to both of the electromagnets and a valve seat is sufficiently reduced so that a shock is relieved. Furthermore, it is necessary to make the power supply turn on-and-off control highly accurate to secure a response characteristic. To achieve the highly accurate control of the armature position, it is necessary to secure a detection accuracy of the armature position by the position sensor.
However, since the armature position is varied in time due to its aging effect caused by wears in each part of the electromagnetically operated engine valve, the detection accuracy on the armature position is reduced.
It is hence an object of the present invention to provide apparatus and method for controlling a position of electromagnetically operated engine valve in which an output signal value of the position sensor to detect the position of the armature common to the pair of electromagnets is appropriately corrected, consequently, the armature position can always be detected with a high accuracy, and a highly accurate control over the open-and-closure position of the electromagnetically operated engine valve can be achieved.
According to one aspect of the present invention, there is provided a control apparatus for an internal combustion engine, comprising: an armature that is associated with an engine valve; a spring to bias the armature at a neutral position which is located at an intermediate position between an open position of the engine valve and a closure position thereof; a first electromagnet to attract the armature toward the open position; a second electromagnet to attract the armature toward the closure position; a position sensor to detect a position of the armature and output a signal indicative of the position of the armature; and a controller that controls the first and second electromagnets responsive to the output signal of the position sensor so that the engine valve is displaced between the open position and the closure position and that corrects the output signal of the position sensor on the basis of two output signals of the position sensor which correspond to two different positions of the engine valve, one of the two different positions being one of the open position and the closure position upon a completion of an initialization prior to an engine start.
According to another aspect of the present invention, there is provided control method for an internal combustion engine, the internal combustion engine comprising: a spring to bias an engine valve at a neutral position which is located at an intermediate position between a full open position of the engine valve and a closure position thereof; a first electromagnet to attract the engine valve toward the full open position and hold the engine valve thereat when energized; a second electromagnet to attract the engine valve toward the closure position and hold the engine valve thereat when energized; and a position sensor to detect a position of an armature which is common to each of the first and second electromagnets and is associated with a valve body of the engine valve and output a signal indicative of the position of the armature and the control method comprising: executing an initialization prior to an engine start for the engine valve; correcting a relationship of an output signal value of the position sensor to a detected value of the position of the armature on the basis of two output signal values of the position sensor which corresponds to two different positions of the engine valve, one of the two different positions being one of the full open position and the closure position after executing the initialization; and being responsive to the output signal of the position sensor to control a turn on-and-off of a power supply to each of the first and second electromagnets so that the engine valve is displaced between the full open position and the closure position.
This summary of the invention does not necessarily describe all necessary features so that the invention may also be a sub-combination of these described features.